Optimum Soil Type

• Raspberries prefer a well-drained, sandy loam soil. Loam is a mixture of sand, silt, clay and organic matter. The designation of sandy loam indicates that the soil has predominantly sand sized particles. Loamy soil is the ideal garden soil because it contains enough sand to promote drainage and enough silt, clay and organic matter to supply necessary nutrients and retain sufficient moisture. If the soil in your garden is not a loam, you can place a 2-inch layer of organic matter over the area and till it into the garden to increase drainage, nutrients and moisture retention.
  
  

Soil pH

• Raspberry plants prefer a slightly acidic soil in the pH range of 5.5 to 6.5. Before you plant raspberry bushes, test your soil using a home soil pH testing kit or employ a laboratory to analyze the soil. If the soil pH is below 5.5, add lime to the soil to raise the pH. Add elemental sulfur to soil with a high pH to lower it into the optimal range. Follow the application rates recommended by the manufacturer to ensure that you achieve a pH of 5.5 to 6.5. You can also use natural materials, such as sphagnum peat, to lower the pH.
  
  

Soil Nutrient Levels

• Proper nutrients are necessary for raspberry plants to thrive in the garden. Everbearing raspberry varieties need approximately 50 percent more fertilizer than the summer-bearing varieties. According to the Colorado State University Extension, quality garden soil requires only 4 lbs. of ammonium sulfate and 2 lbs. of superphosphate for every 1,000 square feet of garden area; however, you should double this amount if the garden does not produce well or if you are unsure if the nutrient levels are appropriate. For nutrient-depleted garden soil, also add 1 lb. each of zinc sulfate and iron chelate and 10 bushels of organic matter before the initial planting of raspberry bushes.
  
  

Soil Moisture Content

• The moisture content of the garden soil is important for raspberries because they like a moist, but not boggy, environment. Adequate organic matter in the soil will help to retain sufficient moisture while allowing extra water to drain away from the root system. During the growing season, keep the plants watered and moist, especially during times of low rainfall. As winter approaches, withhold water after the first frost of the season. Limiting water after the frost begins will begin to harden the plants to withstand the cold weather.